Not Applicable.
Not Applicable.
This invention relates to semiconductor laser diodes, specifically to such semiconductor laser diodes, which have multilayered vertically oriented cavity structures that typically comprise of a substrate used to provide growth foundation, a (LED) xe2x80x9cLight Emitting Diodexe2x80x9d used as pump source and to also provide gain, and two contra-reflecting mirrors used to provide optical feedback and emission wavelength selection.
Semiconductor laser diodes, specifically semiconductor laser diodes having a multilayered vertical cavity structure (i.e., vertical orientation that is perpendicular to the substrate of the semiconductor diode) have become widely known as (VCSELs) xe2x80x9cVertical Cavity Surface-emitting Lasersxe2x80x9d. However, while the present invention uses a vertically oriented LED structure to produce fundamental photonic radiation (i.e., spontaneous stimulation) and to provide gain, its feedback providing optical cavity and the physics that occur therein, are quite different from that of VCSEL laser diodes. Therefore, the present invention should be categorized as a new kind of semiconductor laser diode.
For example, the present invention, by using only one mirror in place of two mirrors to provide feedback, the present invention has redefined vertically orientated cavity design. Inspired by the present invention""s unique optical physics and design, I have named this new semiconductor laser diode, for future identification, the (FCSEL) xe2x80x9cFolded Cavity Surface-emitting Laserxe2x80x9d.
However, at this point I would like to digress by first describing some current trends in vertically oriented laser diode design of which, the most known and widely used is the VCSEL laser diode design. These light sources have been adopted for several applications, such as gigabit-Ethernet in a remarkably short amount of time. Due to their reduced threshold current, circular output beam, inexpensive, and high-volume manufacture, VCSELs are particularly suitable for multimode optical-fiber local-area networks (i.e., LANs).
Moreover, selectively oxidized VCSELs contain an oxide aperture within its vertical cavity that produces strong electrical and optical confinement, enabling high electrical-to-optical conversion efficiency and minimal modal discrimination; allowing emission into multiple transverse optical-modes. Such multi-mode VCSEL lasers make ideal local area network laser light sources. VCSELs that emit into a single optical transverse mode are ever increasingly being sought-out for emerging applications including data communication using single-mode optical fiber, barcode scanning, laser printing, optical read/write data-heads, and modulation spectroscopy. Consequently, achieving single-mode operation in selectively oxidized VCSELs is a challenging task, because the inherent index confinement within these high-performance laser diodes is very large. VCSELs have optical-cavity lengths approximately one-wavelength and therefore, operate within a single longitudinal optical-mode. However, because of their relatively large cavity diameters (i.e., roughly 5.0 to 20.0 micrometers), these laser diodes usually operate in multiple transverse optical-modes, where each transverse optical-mode possesses a unique wavelength and what is called a transverse spatial intensity profile (i.e., intensity pattern).
Moreover, for applications requiring small spot size or high spectral purity, lasing in a single transverse optical-mode, usually the lowest-order fundamental mode (i.e., TEM-00) is desired. In general, pure fundamental mode emission within a selectively oxidized VCSEL can be attained by increasing optical loss to higher-order transverse optical-modes relative to that of the previously mentioned fundamental mode. By selectively creating optical loss for any particular mode, we increase modal discrimination, which consequently leads to a VCSELs operation in a single transverse optical-mode. Strategies for producing VCSELs that operate in single transverse optical-mode have recently been developed.
Furthermore, these strategies are based either on introducing loss that is relatively greater for higher-order optical-modes and thereby, relatively increasing gain for the fundamental transverse optical-mode, or as an alternative, creating greater gain for the fundamental transverse optical-mode. Increased modal loss for higher-order optical-modes has been successfully demonstrated using three different techniques. The first approach to modal discrimination uses an etched-surface relief located on the periphery of the top facet that selectively reduces the reflectivity of the top mirror for higher-order transverse optical-modes. The advantage of this technique is that the ring located around the edge of the cavity, etched in the top quarterwave mirror stack assembly can be produced during the VCSEL""s initial fabrication by conventional dry-etching, or it can be post processed on a completed VCSEL die using focused ion-beam etching. A disadvantage, however, of etched-surface relief is that it requires careful alignment to the oxide aperture and can increase the optical scattering loss of the fundamental transverse optical-mode, as manifested by the relatively low (i.e., less than 2 mW) single-mode output powers that have been reported. Therefore, it would be more desirable to introduce mode-selective loss into the VCSEL""s structure during its epitaxial deposition to avoid extra fabrication steps and to provide self-alignment problems.
Moreover, two such techniques are the use of tapered oxide apertures and extended optical cavities within the VCSEL laser diode. The first approach, which was pursued extensively at Sandia National Laboratories (i.e., Albuquerque, N.Mex.), is predicated on designing the profile of the oxide aperture tip in order to preferentially increase loss for higher-order transverse optical-modes. The aperture-tip profile is produced by tailoring the composition of the (AlGaAs) xe2x80x9cAluminum-Gallium-Arsenidexe2x80x9d layers, which are oxidized during fabrication to create an aperture located within the before mentioned VCSEL. A VCSEL containing a tapered oxide whose tip is vertically positioned at a null in the longitudinal optical standing wave can produce greater than 3-mW of single-mode output, and greater than 30-dB of side-mode suppression. Creating this structure, however, requires a detailed understanding of the oxidation process, and produces additional loss for the fundamental transverse optical-mode, as well.
In addition, a second way to increase modal discrimination is to extend the optical cavity length of VCSEL itself and thus, increase the diffraction loss for the higher-order transverse optical-modes. Researchers at the University of Ulm (i.e., Ulm, Germany) have reported single-mode operation up to 5-mW, using a VCSEL constructed with a 4-micrometer thick cavity spacer inserted within the optical-cavity. The problem, however, is that by using even-longer cavity spacers can also introduce multiple longitudinal optical-modes (i.e., what is sometimes called spatial hole burning), but single-transverse-optical-mode operation up to nearly 7-mW has been demonstrated. It is interesting to note that VCSELs containing multiple wavelength cavities do not appear to suffer any electrical penalty, although careful design is required to balance the trade-offs between the modal selectivity of the transverse and the longitudinal optical-modes.
Finally, manipulating the modal gain rather than loss can also produce single-mode VCSELs. A technique, designed to spatially aperture laser-gain independently of the oxide aperture has been developed at Sandia National Laboratories. The essential aspect of these VCSELs is the lithographically defined gain region, which is produced by an intermixing of quantum-well active regions at the lateral periphery of the VCSEL""s laser cavity. Typically, fabrication processes for a typical VCSEL laser diode begins with an epitaxial growth of the VCSEL""s bottom (DBR) xe2x80x9cDistributed Bragg Reflectorxe2x80x9d based quarterwave mirror-stack assembly onto an optical or semiconductor substrate. After which, the VCSEL""s active-region (i.e., a multiple quantum well containing double-heterostructure) is epitaxially grown onto the top outermost surface of the bottom DBR. Finally, the VCSEL""s top DBR quarterwave mirror-stack assembly is epitaxially grown onto the top outermost surface of the active-region.
In addition, a VCSEL""s quantum wells are homogenized by ion-implantation around the masked regions that were used to create the cavity forming second DBR quarterwave mirror-stack assembly, during epitaxial material deposition. The resultant VCSEL has a central quantum-well active-region that preferentially provides gain for the fundamental mode. Consequently, for this approach only a single-mode output of more than 2-mW with a side-mode-suppression ratio greater than 40-dB is obtained. This approach also requires greater fabrication complexity, however, it is anticipated that higher performance can be reached with further refinement of process parameters. Because of the new and greater demands of VCSEL applications, new types of single-mode VCSELs are currently under development at numerous laboratories around the world. The techniques demonstrated to date introduce modal discrimination by increasing optical loss for the higher-order modes, or as an alternative, by increasing the relative gain of the fundamental optical-mode.
In addition, to better understand the structural differences between the present FCSEL invention and prior art VCSEL technology, a typical VCSEL design is presented as an example of prior art. As illustrated in FIGS. 1, 2, and 3, a typical VCSEL uses a process of recombining radiation (i.e., sometimes called xe2x80x9cradiative recombinationxe2x80x9d) to produce fundamental intra-cavity light, which, during multiple oscillations through a VCSEL""s cavity containing active-region, is ultimately amplified into coherent laser emission. Prior art, as illustrated in FIGS. 1, 2, and 3 is an example of a high-frequency VCSEL laser diode design that uses a metallic supporting substrate 22 (FIG. 1) as both a base-reflecting mirror structure 22 (FIG. 2) and a substrate used for the subsequent epitaxial growth of multilayered structures. The substrate material is where a VCSEL typically begins its multi-layered construction, using epitaxial growth processes, such as molecular beam epitaxy (MBE) or metallic-organic chemical vapor deposition (MOCVD) to expedite deposition of optical and semiconductor construction material.
Furthermore, a VCSEL""s metallic supporting substrate 22 (FIG. 3), when conductive, as an alternative embodiment, would serve as the VCSEL(s) electrically negative electrode. The metallic supporting substrate 22 that comprises a (Nixe2x80x94Al) xe2x80x9cNickel-Aluminumxe2x80x9d alloy-mixture which has between an xe2x80x9c8.0xe2x80x9d to a xe2x80x9c12.0xe2x80x9d percent material lattice-mismatch, or more specifically a xe2x80x9c10.0xe2x80x9d percent material lattice-mismatch to the binary (GaN) xe2x80x9cGallium-Nitridexe2x80x9d semiconductor material deposited later. Nevertheless, despite (Nixe2x80x94Al) xe2x80x9cNickel-Aluminumxe2x80x9d lattice-mismatch it is still the preferred metallic alloy-mixture for this kind of electron conducting metallic supporting substrate 22. In addition, the (Nixe2x80x94Al) xe2x80x9cNickel-Aluminumxe2x80x9d metallic supporting substrate 22 (FIG. 3), if used as an alternative embodiment, would also need to exhibit a highly reflective property as well and, therefore should have a surface roughness of less than xe2x80x9c15xe2x80x9d atoms thick.
Furthermore, as illustrated in FIGS. 1, 2, and 3, prior art shows that several layers of (AlN) xe2x80x9cAluminum-Nitridexe2x80x9d can be epitaxially grown, using MBE or MOCVD to create a single buffer-layer 23 (FIG. 3) with a thickness of only a few atoms. The AlN buffer-layer is used next for facilitating the MBE or MOCVD epitaxial growth of the many subsequent layers that will comprise a single VCSEL device. As illustrated in FIGS. 1, 2, and 3 prior art also shows that a VCSEL has its first DBR quarterwave mirror-stack assembly 24 epitaxially deposited onto the top outermost surface of the previously deposited buffer-layer 23A, 23B, 23C, 23D (FIG. 3) of (AlN) xe2x80x9cAluminum-Nitridexe2x80x9d material, using any suitable epitaxial crystal growing method, such as MBE or MOCVD.
In addition, as illustrated in FIGS. 1, 2, and 3 prior art also shows that a VCSEL""s first DBR quarterwave mirror-stack assembly 24 is made from a plurality of alternating layers comprised as mirror-pairs; or more precisely is made from a multitude of single pairs of alternating layers 24A, 24B (FIG. 3) that are constructed from (GaN/AlGaN) semiconductor materials, and used to complete a single mirror-pair. The plurality of alternating layers used to comprise the multitude of mirror-pairs, will include one or more layers of N-doped (GaN) xe2x80x9cGallium-Nitridexe2x80x9d 24A, 24C, 24E, 24G, 24I (FIG. 3) a high-refractive semiconductor material, and N-doped (AlGaN) xe2x80x9cAluminum Gallium Nitridexe2x80x9d 24B, 24D, 24F, 24H, 24J (FIG. 3) a low-refractive semiconductor material.
For example, as illustrated in FIGS. 1, 2, and 3 prior art shows that a layer 24A of N-doped (GaN) xe2x80x9cGallium-Nitride is epitaxially deposited onto the top and outermost surface of a VCSEL""s buffer-layer 23 (FIG. 3), while a layer 24B (FIG. 3) of N-doped (AlGaN) xe2x80x9cAluminum Gallium Nitridexe2x80x9d is subsequently and epitaxially deposited onto the top and outermost surface of the VCSEL""s first N-doped (GaN) xe2x80x9cGallium-Nitride layer 24A (FIG. 3). If additional mirror-pairs are required, several more layers that make-up additional mirror-pairs can be deposited onto existing layers of (GaN) xe2x80x9cGallium-Nitride and (AlGaN) xe2x80x9cAluminum Gallium Nitridexe2x80x9d materials 24A, 24B, 24C, 24D, 24E, 24F, 24H, 24I (FIG. 3).
Moreover, to increase the reflectivity of a VCSEL""s first DBR quarterwave mirror-stack assembly 24 (FIG. 3) to the required amount of reflectance, many additional mirror-pairs will be required, and depending upon the wavelength of light being reflected, as many as several hundred mirror-pairs might be needed and used within a single VCSEL laser diode. It should be understood that the thickness and doping levels of each deposited layer used to construct a VCSEL laser diode is precisely controlled. Any deviation from designed parameters, no matter how slight, would affect the performance of the VCSEL in question (e.g., frequency range, flux intensity).
For example, as illustrated in FIGS. 1, 2, and 3, prior art shows that the VCSEL""s emitter-layer 33, which is designed to emit laser-light having a wavelength of xe2x80x9c200xe2x80x9d nanometers, should have a material thickness that is one quarter of one wavelength of the VCSEL""s laser emission. Which is altogether true for each of the other alternating layers that comprise both of the VCSEL""s DBR quarterwave mirror-stack assemblies 24, 32 (FIG. 3). As illustrated in FIGS. 1, 2, and 3, prior art shows that all of the alternating layers used to comprise a VCSEL""s first and second DBR quarterwave mirror-stack assemblies 24, 32 (FIG. 3) should have a material thickness of xe2x80x9c50xe2x80x9d nanometers.
Furthermore, as illustrated in FIGS. 1, 2, and 3 prior art shows that to prevent the overcrowding of the cladding-layers located within a VCSEL""s active-region 28 (FIG. 3), each of two cladding-layers 28A, 28C (FIG. 3) are shown here as being contra-located onto opposite sides of a single active-area 28B. Each illustrated cladding-layer 28A, 28C (FIG. 3) is epitaxially deposited onto a previously deposited layer, the last layer used in constructing the first DBR and the last layer used in constructing the active-area, respectfully. Each cladding-layer 28A, 28C is comprised from N-doped or P-doped (AlGaN) xe2x80x9cAluminum-Gallium-Nitridexe2x80x9d ternary semiconductor material, respectfully.
Therefore, as illustrated in FIGS. 1, 2, and 3 prior art shows that after the plurality of alternating layers used in a VCSEL""s first DBR quarterwave mirror-stack assembly 24 have been deposited onto the top and outermost surface of the VCSEL""s buffer-layer of (AlN) xe2x80x9cAluminum-Nitridexe2x80x9d 23, then the VCSEL""s first contact-layer 25 (FIG. 3) comprising a highly +n-doped (GaN) xe2x80x9cGallium-Nitridexe2x80x9d binary semiconductor material can be epitaxially grown onto the top and outermost surface of the last alternated layer of the VCSEL""s first DBR quarterwave mirror-stack assembly 24 (FIG. 3). A VCSEL""s first contact-layer 25, while providing connectivity to the VCSEL""s n-metal contact 27 (FIG. 3) and to the VCSEL""s n-metal contact-ring 26 (FIG. 1), will also enhance the reliability of the VCSEL""s design by preventing the migration of carrier-dislocations, and the like to the VCSEL""s active-region 28 (FIG. 3).
Furthermore, as illustrated in FIGS. 1, 2, and 3 prior art shows that to prevent the overcrowding of the cladding-layers located within a VCSEL""s active-region 28 (FIG. 3), each of two cladding-layers 28A, 28C (FIG. 3) are shown here as being contra-located onto opposite sides of a single active-area 28B. Each illustrated cladding-layer 28A, 28C (FIG. 3) is epitaxially deposited onto a previously deposited layer, the last layer used in constructing the first DBR and the last layer used in constructing the active-area, respectfully. Each cladding-layer 28A, 28C is comprised from N-doped or P-doped (AlGaN) xe2x80x9cAluminum-Gallium-Nitridexe2x80x9d ternary semiconductor material, respectfully.
Furthermore, as illustrated in FIGS. 1, 2, and 3 prior art also shows that a VCSEL""s active-region 28 (FIG. 3), which is shown here as being represented by a single (SQW) xe2x80x9cSingle Quantum Wellxe2x80x9d layer that is epitaxially deposited onto the top and outermost surface of the VCSEL""s first cladding-layer 28A (FIG. 3) (i.e., sometimes called a cladding-barrier). It should be understood, however, that a VCSEL""s active-area 28 (FIG. 3) could also include one or more quantum-well cladding-layers and quantum-well layers, as is typical of MQW structure; particularly, a first quantum-well cladding-layer and a second quantum-well cladding-layer, with a quantum-well layer positioned between the first quantum-well cladding-layer and a second quantum-well cladding-layer. As illustrated in FIGS. 1, 2, and 3 prior art shows that a VCSEL""s active-area 28B (FIG. 3) comprises as a SQW, which is constructed from a p-doped (InGaN) xe2x80x9cIndium-Gallium-Nitridexe2x80x9d extrinsic ternary semiconductor material, while using MBE or MOCVD to epitaxially deposit the material.
In addition, as illustrated in FIGS. 1, 2, and 3 prior art also shows that a VCSEL""s second contact-layer 29 (FIG. 3) is comprised from a highly +p-doped (GaN) xe2x80x9cGallium-Nitridexe2x80x9d extrinsic binary material that is epitaxially grown onto the top and outermost surface of the VCSEL""s second cladding-layer 28C (FIG. 3). A VCSEL""s second contact-layer 29, while providing connectivity to the VCSEL""s p-metal contact 31 (FIG. 3) and to the VCSEL""s p-metal contact-ring 30 (FIG. 1), will also enhance the reliability of the VCSEL""s design by preventing the migration of carrier-dislocations, and the like to the VCSEL""s active-region 28 (FIG. 3).
Furthermore, when constructing a VCSEL""s electrical contacts, it should be understood that the choice of one method of material deposition over another depends solely upon which construction material is selected. Therefore, specific methods of disposition, disposing, and patterning onto the VCSEL""s first and second contact-layers 25, 29 (FIG. 3), for any specified material, must be considered in the construction of the VCSEL""s electrical contacts. As illustrated in FIGS. 1, 2, and 3 prior art also shows that a VCSEL""s second contact-layer 29 (FIG. 3), the VCSEL""s second cladding-region 28C, the VCSEL""s active-area 28B, and the VCSEL""s first cladding-layer 28A (FIG. 3) are all mesa-etched. The process of mesa-etching, which ultimately defines the shape and structure of a VCSEL""s lower layers, by causing diameter dimensions to remain substantially larger than the VCSEL""s second DBR quarterwave mirror-stack assembly 32 (FIG. 2) and topmost emitter-layer 33 (FIG. 1) the second DBR supports. When mesa-etching and ion implantation steps are completed, a VCSEL""s p-metal contact 31 (FIG. 3), and the VCSEL""s p-metal contact-ring 30 are deposited onto the top and outermost surface of the VCSEL""s second contact-layer 29, leaving the emitter-layer open 33 (FIG. 3).
Moreover, if additional mirror-pairs are required, several more layers that make-up additional mirror-pairs could be deposited onto the existing layers of (Al2O3) xe2x80x9cAluminum Oxidexe2x80x9d and (ZnO) xe2x80x9cZinc Oxidexe2x80x9d materials 32A, 32B, 32C, 32D, 32E, 32F, 32G, 32H, 32I (FIG. 3). To increase the reflectivity of a VCSEL""s second DBR quarterwave mirror-stack assembly 32 (FIG. 3) to the required amount of partial-reflectance, many additional mirror-pairs will be required, and depending upon the wavelength of light being reflected, as many as several hundred mirror-pairs might be required and used to create a single mirror-stack assembly. Additionally, as illustrated in FIGS. 1, 2, and 3 prior art also shows that a VCSEL""s emitter layer 33, which is constructed from undoped (ZnO) xe2x80x9cZinc-Oxidexe2x80x9d high-refractive dielectric material is the last layer to be epitaxially deposited in the example VCSEL device.
In addition, as illustrated in FIGS. 1, 2, and 3 prior art shows that a VCSEL""s p-metal contact 31 (FIG. 3), and the VCSEL""s p-metal contact-ring 30 (FIG. 3) are typically formed onto the top and outermost surface of the VCSEL""s second contact-layer 29 (FIG. 3), by disposing any suitable conductive material, such as Indium-Tin-Oxide, Gold, Zinc, Platinum, Tungsten, or Germanium metallic alloys. As illustrated in FIGS. 1, 2, and 3 prior art also shows that a VCSEL""s n-metal contact 27 (FIG. 1) and the VCSEL""s n-metal contact-ring 26 (FIG. 2) are typically formed onto the top and outermost surface of the VCSEL""s first contact-layer 25 (FIG. 3), by disposing any suitable conductive material, such as Indium-Tin-Oxide, Gold, Zinc, Platinum, Tungsten, or Germanium metallic alloys.
Furthermore, when constructing a VCSEL""s electrical contacts, it should be understood that the choice of one method of material deposition over another depends solely upon which construction material is selected. Therefore, specific methods of disposition, disposing, and patterning onto the VCSEL""s first and second contact-layers 25, 29 (FIG. 3), for any specified material, must be considered in the construction of the VCSEL""s electrical contacts. As illustrated in FIGS. 1, 2, and 3 prior art also shows that a VCSEL""s second contact-layer 29 (FIG. 3), the VCSEL""s second cladding-region 28C, the VCSEL""s active-area 28B, and the VCSEL""s first cladding-layer 28A (FIG. 3) are all mesa-etched. The process of mesa-etching, which ultimately defines the shape and structure of a VCSEL""s lower layers, by causing diameter dimensions to remain substantially larger than the VCSEL""s second DBR quarterwave mirror-stack assembly 32 (FIG. 2) and topmost emitter-layer 33 (FIG. 1) the second DBR supports. When mesa-etching and ion implantation steps are completed, a VCSEL""s p-metal contact 31 (FIG. 3), and the VCSEL""s p-metal contact-ring 30 are deposited onto the top and outermost surface of the VCSEL""s second contact-layer 29, leaving the emitter-layer open 33 (FIG. 3).
In addition, the deposition of a VCSEL""s n-metal contact 27, as an alternative embodiment, can be deposited onto the top and outermost surface of a VCSEL""s metallic substrate 22 (FIG. 3) of (NiAl) xe2x80x9cNickel-Aluminumxe2x80x9d alloy. Allowing, the total metallic substrate 22 to function as an electrically negative contact-layer. As illustrated in FIGS. 1, 2, and 3 prior art also shows that a VCSEL""s metallic substrate 22 (FIG. 3), when it is used in conjunction with the VCSEL""s first DBR quarterwave mirror-stack assembly 24, and because the VCSEL""s first DBR quarterwave mirror-stack assembly 24 (FIG. 3) is constructed from highly-reflective (AlGaN/GaN) xe2x80x9cAluminum-Gallium-Nitride/Gallium-Nitridexe2x80x9d, both it and the VCSEL""s metallic substrate 22 (FIG. 3) will provide approximately xe2x80x9c99.99xe2x80x9d percent of the VCSEL""s total reflectivity. Additionally, illustrated in FIGS. 4, 5, and 6 is an example of how typical VCSEL laser diodes can be grouped together and configured into a linear array of laser diodes.
In accordance with the present invention, a folded cavity surface-emitting laser will comprise a cavity folding waveguide structure having at least one total internally reflecting prism providing for the redirection of intra-cavity produced fundamental photonic radiation into and out of transverse propagation within a single lengthened optical cavity, a double-heterojunction semiconductor diode active-region having an active-area providing for both the production and amplification of fundamental photonic radiation, a partial photon reflecting structure capable of reflecting sufficient undiffused optical radiation, providing input for the semi-reflected feedback and partial-reflected output of intra-cavity produced amplified photonic radiation.
Objects and advantages of the present invention are:
(a) To provide a surface-emitting semiconductor laser diode that creates light amplifying feedback with only one quarterwave mirror-stack assembly, and a cavity folding internal reflecting polyhedral prism waveguide that comprises a single layer of dielectric material;
(b) To provide a surface-emitting semiconductor laser diode that is inexpensive to manufacture, which is accomplished by eliminating the expensive epitaxial deposition of a bottom quarterwave mirror-stack assembly comprising a multitude of layered dielectric or semiconductor materials, and replacing it with a dielectric polyhedral prism waveguide inexpensively constructed using a single sputtered or epitaxially deposited layer;
(c) To provide a surface-emitting semiconductor laser diode that uses two graded confinement cladding-layers to optically confine its active-area, increasing emission output exhibiting a narrower linewidth;
(d) To provide a surface-emitting semiconductor laser diode that produces more effective output gain by using two graded confinement cladding-layers to lower the heat producing electrical resistance that normally occurs between contact-layers and cladding-layers;
(e) To provide a surface-emitting semiconductor laser diode that increases optical confinement of its cavity with the addition of total internal-reflecting cladding material to the outermost wall surfaces of the laser diode""s mesa-etched folded vertical cavity(s);
(f) To provide a surface-emitting semiconductor laser diode that can be configured and utilized as a single laser device;
(g) To provide a surface-emitting semiconductor laser diode that can be configured and utilized in a single laser-array comprising a multitude of individual laser diodes, which are individually addressable or together, addressable as a single group;
(h) To provide a surface-emitting semiconductor laser diode or a surface-emitting semiconductor laser diode-array that can be manufactured at the same time and from the same semiconductor substrate material used to construct a laser-array""s control-circuitry, all of which would be contained within a single semiconductor device;
(j) To provide a surface-emitting semiconductor laser diode that replaces a bottom quarterwave mirror-stack assembly with a polyhedral prism waveguide which, if comprised of quartz or fused silica can reflect xe2x80x9c100xe2x80x9d percent, using a process of total internal-reflection, all wavelengths of optical radiation that enters the polyhedral prism waveguide""s top front-face flat horizontal-surface;
(k) To provide a surface-emitting semiconductor laser diode that can inexpensively construct its polyhedral prism waveguide using a well-known ion-milling process to slice out prism facet(s) comprising the polyhedral prism waveguide""s structure;
(l) To provide a surface-emitting semiconductor laser diode that can deposit a dielectric material, such as fused-silica, onto any light producing wide-bandgap semiconductor material, or combination thereof, which could possibly be used in the construction of a single surface-emitting semiconductor laser diode or a single surface-emitting semiconductor laser diode array;
(m) To provide a surface-emitting semiconductor laser diode that uses an amorphous material, such as xe2x80x9cLithium-Fluoridexe2x80x9d to construct, for mesa-etched vertical cavity(s), an optical-cladding total internal-reflecting material, which would also give added support to the polyhedral prism waveguide(s);
(n) To provide a surface-emitting semiconductor laser diode that can increase its modal discrimination by extending its optical-cavity length, using a polyhedral prism waveguide to transversely redirect intra-cavity produced light to new areas of the diode""s gain-region previously un-stimulated;
(o) To provide a surface-emitting semiconductor laser diode that can increase its modal discrimination, using a process of total internal-reflection to redirect intra-cavity produced light out of its normal longitudinal propagation into a first transverse propagation, then next into a second transverse propagation, then next into a third transverse propagation, and then finally into a longitudinal, but reversed propagation, which will effectively increase diffraction loss for higher-orders of transverse optical-moded light, while sufficiently increasing gain to the fundamental lower-order transverse optical-moded light causing it to undergo amplification into laser emission;
(p) To provide a surface-emitting semiconductor laser diode that has eliminated from its structure lattice-matched crystal growing buffer-layers, which are normally constructed using materials such as xe2x80x9cAluminum-Nitridexe2x80x9d;
(q) To provide a surface-emitting semiconductor laser diode that produces at least an increase of nearly 7-mW for fundamental lower-order single-transverse optical-moded light;
Further objects and advantages are to provide a surface-emitting semiconductor laser diode, where selection of one semiconductor material over another, or more particularly, selection of one optical material over another for use in the construction of a FCSEL""s active-region, a FCSEL""s polyhedral prism waveguide, and a FCSEL""s multilayered quarterwave mirror-stack assembly is not determined by a FCSEL""s geometry or any other structural criteria, but is determined by a particular application""s need for a specific wavelength(s).
Therefore, as presented here within this specification, the materials chosen for constructing the present FCSEL invention are presented here as only one example of several possible wavelength-specific semiconductor materials that might, or could be used to construct the present invention""s wavelength transcendent structure. The advantages that are provided by novel features and un-obvious properties lie within a FCSEL""s cavity-folding structure, and not within any particular material regime.
However, because the FCSEL""s novel features and un-obvious properties can exist or occur using any wavelength-specific semiconductor or optical material regime, clearly shows that the various structures comprising the FCSEL laser diode, have both sufficient novelty and a non-obviousness that is independent of any one material regime that might, or could be used in the construction of a FCSEL laser diode(s).